Coaxial switch



y 1968 R. D. MCCLAFLIN ETAL 3,394,324

COAXIAL SWITCH Filed July 31, 1962 iii-J 32 33 8 Fi -L7 36 as IT i 1 ROBERT D. h fi f'm TED N. TILMAN WWQW AGENT United States Patent "ice 3,394,324 COAXIAL SWITCH Robert D. McClaflin and Ted N. Tilman, San Jose, Calif.,

assignors t0 Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of Delaware Filed July 31, 1962, Ser. No. 213,692 3 Claims. (Cl. 333-97) The invention relates to coaxial switches, and particularly to a coaxial switch for UHF frequencies.

It is one of the objects of the present invention to provide a coaxial switch of single pole-double throw configuration which incorporates an impedance matching ground plane within the envelope.

Another object of the invention is the provision of a coaxial switch operating in the frequency range between 300 and 3000 megacycles.

A still further object of the invention is the provision of a coaxial switch capable of operation at high RF voltages and UHF frequencies.

Still another object of the invention is the provision of a coaxial switch capable of operation in the frequency range from zero to 1500 megacycles and requiring no tuning throughout this frequency range.

A still further object of the invention is the provision of a coaxial switch which incorporates three metallic leads extending into a dielectric envelope, the three leads constituting a part of a constant impedance ground plane extending through the switching chamber and adapted to be connected to the external conductor of an associated coaxial transmission line.

Another object of the invention is the provision of three additional leads extending into the envelope intermediate the ground potential leads to constitute high potential contacts adapted to be connected to the center conductors of three associated coaxial transmission lines, one such contact being common to adjacent normallyopen and normally-closed contacts of the coaxial switch.

The invention possesses other objects, some of which, with the foregoing. will be brought out in the following description of the invention. The invention is not limited to the showing made by the said description and the drawings, since it may be embodied in variant forms within the scope of the appended claims.

Referring to the drawings:

FIG. 1 is a vertical half-sectional view taken in the plane indicated by the line 1 1 of FIG. 2 and showing the invention embodied in a single pole-double throw switch.

FIG. 2 is a horizontal sectional view taken in the plane indicated by the line 2-2 of FIG. 1.

FIG. 3 is a horizontal sectional view similar to FIG. 2 but with a portion of the ground plane structure removed to more clearly disclose the underlying parts.

FIG. 4 is a fragmentary view illustrating the preferred relationship of impedance matching members and high potential contacts within the envelope.

FIG. 5 is a fragmentary view illustrating a modified embodiment of the impedance matching structure.

FIG. 6 is a fragmentary view illustrating another modified embodiment of the impedance matching structure.

FIGS. 1, 2 and 3 are shown approximately twice actual size, and FIGS. 4, 5 and 6 are shown approximately four times actual size.

Broadly considered, the coaxial switch of the invention comprises an hermetically sealed envelope formed by a dielectric envelope portion or bulb closed on at least one side by a metallic endwall and together defining an hermetically sealed switching chamber. Mounted on the metallic wall is a magnetizable core having an inner end adjacent the metallic wall. Within the chamber, an arma- 3,394,324 Patented July 23, 1968 ture is pivotally mounted for movement toward and away from the inner end of the core, and a selectively energizable coil is provided adjacent the end of the core remote from the armature operable to selectively move the armature toward the core. A coil spring within the chamber interposed between the armature and the metallic wall operates to urge the armature away from the inner end of the core. Within the chamber and mounted on the dielectric envelope portion or bulb wall are a plurality of spaced terminal leads, each of which is continuous with a lead portion external to the envelope. In the present instance there are preferably six such leads extending radially into the envelope, three of the leads terminating in spaced high potential contact points within the switching chamber. A movable contact member within the chamber normally continuously engages one of the contact points, and is rollably movable thereon into and out of engagement with another contact point to make or break a circuit therebetween. Such contact points engageable by the movable contact are conveniently spaced apart, and each constitutes the terminal end of the inner conductor of a coaxial transmission line. Disposed between each pair of inner conductor contacts is another conductive lead which constitutes a ground potential terminal lead for connection to the outer conductor of an associated coaxial transmission line. Conductive metallic impedance-matching ground plane means are provided conductively connecting the last mentioned terminal leads within the envelope. A resilient stem structure is provided mounting the movable contact on the armature and for insulating it therefrom.

In terms of greater detail, the coaxial switch of the invention comprises an envelope including a dielectric portion 2, closed at one end by a metallic wall including a hollow conical copper flange 3 having one end hermetically bonded to the open end of the dielectric envelope portion, and its other outer end brazed about the periphery of a hollow metallic housing extends into the copper flange, and the outer end of the housing is provided with external threads 7 useful to mount the switch in a panel. The threads may be formed directly in the housing wall as shown, or they may be formed in the periphery of a sleeve 8, which is then brazed about the outer end of the housing.

Within the hollow housing and transversely interposed intermediate the ends thereof is an annular non-magnetic plate 9 having its outer periphery hermetically brazed to the housing wall. A magnetizable core 12, coaxially aligned with the housing, extends through the central aperture of the annular plate and is hermetically brazed therein. The inner end 13 of the core lies adjacent the nonmagnetic plate 9 and cooperates with the inner end 6 of the magnetizable housing to form a magnetic circuit normally having a gap 14 therein. The core extends outwardly from the plate 9 through the housing and terminates flush with the outer end of the housing. An energizable coil 15, mounted on a cover plate 16 and fitting snugly within the hollow housing, surrounds the outer end of the core and is detachably secured thereon by a nut 17 which clamps the cover plate tightly against the outer ends of the core and housing, thus completing a magnetic path at this end of the housing. Coil leads 18 extending through the cover plate serve to connect the coil in a control circuit operable to energize the coil and magnetize the core.

A common problem in the manufacture of devices of the type disclosed is the exclusion of contaminants from within the envelope before it is hermetically sealed. One method commonly used is to apply an acid rinse to the interior of the envelope. This method is efiective, but it is diflicult to avoid trapping some of the cleaning solution 3 within the envelopeTo obviate this costly procedure, we have devised a=construction which permits cleaning of the parts before assembly, and subsequent sealing of the envelope so as to preclude entry of contaminants as a result of the sealing process. Hermetically brazed about the outer end of the copper flange 3 is an annular, radially extending nickel flange 19, the outer periphery 21 of which lies flush with the outer periphery 22 of a second nickel flange 23 brazed about the cylindrical housing 4 when the parts are brought into assembled relationship. The outer peripheries 21 and 22 are heliarc welded, forming a rigid and hermetic union. Evacuation of the envelope, or charging with a suitable gas when it is desired to provide a gasfilled envelope, is then accomplished through tubulation 24 in the closed end of theenvelope portion 2. Joining the enevlope portion and housing assembly by this means makes practicable subsequent opening and re-use of the envelope. This may be accomplished by grinding off the peripheral edges of the flanges until the seal is broken to permit separation of the dielectric envelope portion from the housing assembly. I

In the described embodiment of the invention an evacuated envelope is illustrated and three sets of tungsten contact terminals are provided, each set including a radially extending high potential contact portion 26 circumferentially spaced 120 from corresponding high potential contacts of the other two adjacent sets. These high potential contacts constitute terminations of the center or inner conductors of associated coaxial transmission lines (not shown) which are appropriately connected to integral lead portions 27 extending out of the envelope.

Each set of contacts also includes at least one ground potential lead extending radially into the envelope in a portion 29 and having a portion 31 outside the envelope for connection to the outer conductor of an associated coaxial transmission line (not shown). As shown, the three ground potential leads are electrically connected together in a common ground plane by a pair of oppositely disposed annular ground or impedance matching plates 32, conveniently of .005" nickel, integrally supported on the ground potential lead portions 29 and capacitively associated with each high potential contact. Each ground plate is preferably formed with radially extending convolutions 33 corresponding in circumferential spacing to the spacing of the ground lead portions 29. The radius of each convolution 33 is conveniently proportioned to snugly receive the associated end of the ground lead portion 29 and is welded thereto as by spot welding. Forming the convolution 33 so that it snugly embraces a peripheral surface of the ground lead portion also results in the parts being self-jigging. It will be understood of course that where separate jigging means are provided the convolutions 33 may be formed with a much larger radius so that only a line contact is made with the ground leads, or alternatively, the convolutions of the opposed ground plates may be proportioned to completely envelop the ground lead portions. These embodiments are illustrated in FIGURES 4, and 6.

A second set of radially extending convolutions 34 are formed in the opposed ground plates, these convolutions lying at circumferentially spaced intervals corresponding to the spacing of high potential contacts 26 and lying between the convolutions 33, as shown best in FIG. 2. As shown in FIGURE 4, these convolutions are proportioned to provide an annular space 36 between the high potential contact and the ground plate. Capacitance is therefore provided between the high potential contacts and the ground plates, the amount of capacitance being controlled to provide constant impedance transmission through the switch to match the impedance of the associated coaxial transmission lines.

In the embodiment illustrated, there are three high potential contacts 26. One of them, together with the ground leads on opposite sides thereof, constitutes a common coaxial terminal. The other two high potential con- 4 s tacts, with the associated ground leads, constitute, respectively, normally-open and normally-closed coaxial terminals. Means are providedto selectively make or break a circuit through the common terminal and one or the other of the normally-open or normally-closed coaxial terminals.

Pivotally mounted within the evacuated chamber on the inner end 6 of the housing is an armature 37 having a coil spring 38 thereunder interposed between the armature and metallic plate 9, to normally pivot the arm-ature away from the inner end of the core and housing. Energizing the coil 15 imposes a strong magnetic pull on the armature, pivoting it to close the gap 14 between core and housing, and compressing the coil spring 38. Deenergizing the coil releases the armature which is rapidly pivoted outwardly away from the core by the spring 38.

The extremely rapid operation of the switch, being about ten milliseconds for the single pole, device shown, is due in part to the fact that spring 38 imposes minimum resistance against the initial movement of the armature at the instant the coil is energized. As the armature approaches the core and housing, the magnetic force pulling the armature down increases much more rapidly than the buildup of spring pressure tending to push the armature away. When the armature has abutted the housing and core, the magnetic field strength is at its peak and the spring is fully loaded. Deenergizing the coil releases the armature and permits the spring to rapidly pivot the armature outwardly.

Mounted on the armature is a resilient stem structure including a tungsten rod 39 integrally fixed at one end on the armature and extending away therefrom substantially perpendicularly to terminate in a free end 40 spaced from the armature. Mounted on the tungsten rod adjacent its free end is a U-shaped metal bracket 41 having a pair of transversely extending arms 42 and 43. Each of the arms is apertured to receive a non-conductive dielectric rod 44 extending through the apertures and terminating adjacent the inner ends of the high potential leads 26. The ceramic rod lies parallel to tungsten rod 38, and lies closely adjacent the armature. On either side of the arms 42 and 43, the ceramic stem is provided with split springrings 45 to retain the ceramic rod against axial displacement with respect to the bracket.

Rotatably mounted on the ceramic rod adjacent its free end is a rotatable contact member 46 having a cylindrical outer peripheral contact surface portion 47. The contact member is adapted to rotate on the ceramic rod, and is prevented from axial displacement thereon by split springrings resiliently clamped on the rod on opposite sides of the contact.

In the position of the movable contact member shown in FIGURE 1, the spring under the armature has caused the rotatable contact member to connect the high potential common contact and the normally-closed high potential contact appearing at the right in FIG. 1. It will be seen that the contact member is resiliently held against the common contact and the right hand con-tact by operation of the spring under the armature. This results in low contact resistance between the high potential contact and the rolla'ble contact member. Energizing the coil to pivot the armature against the spring swings the stem and movable contact transversely to the left, in FIG. 1. Since the parts are proportioned to effect a resilient contact pressure between the rollable contact member and the common high potential contact point, transverse movement of the rollable contact causes the contact member to roll on the common high potential contact point. This rolla ble relationship between the parts results in a minimum amount of restriction to transverse movement of the movable contact, thus eflecting an increase in the operating speed of the switch, and reducing the tendency of the contact member to bounce. In this regard, the length of the dielectric rod is of some importance since it permits a relatively long excursion of the movable contact for only a small movement of the armature, again increasing the operating speed of the switch. A longer excursion also permits wider spacing of the high potential contact points, thus increasing the internal Voltage breakdown rating of the switch.

'In the embodiment illustrated, it will be noted that the inner end of each high potential contact 26 is provided with a chisel point which reduces the area of contact adjacent the rolla'ble contact member. It has been found that forming the end of the contact in this manner reduces the capacitance between the open coaxial contact and the movable contact member and thus reduces crosstalk between the closed and open circuits.

It will, of course, be understood that the switch described above is adapted to be used with appropriate commercially available coaxial transmission line con nectors (not shown) which connect to leads 27 and 31 outside the evacuated envelope. The voltage standing wave ratio of the associated transmission line is maintained constant through the evacuated envelope wall and switch in a manner to substantially eliminate a mismatch of impedance between the coaxial transmission line and the coaxial switch.

It should also be understood that while a single poledouble throw configuration has been described and illustrated in conjunction with an evacuated envelope, the invention may be embodied in other configurations and in a gas filled envelope without departing from the scope of invention as defined by the appended claims.

We claim:

1. A coaxial switch comprising a dielectric envelope portion closed on one side with a metallic wall and therewith enclosing a hermetically sealed chamber, a magnetic core fixed on the metallic wall and having one end adjacent thereto, an armature pivotally mounted Within the chamber adjacent one end of the core, means pressing the armature in a direction away from the core, means adjacent the end of the core remote from the armature operable to move the armature in a direction toward the core, spaced contact points within the chamber mounted on the dielectric envelope portion, each said point being continuous with a lead external to the envelope portion, a movable contact engaging one of the contact points and movable into and out of engagement with another contact point to close a circuit therebetween, means mounting the movable contact on the armature for movement therewith, and ground-plane means within the dielectric portion of the envelope electrically insulated with respect to the contact points and extending uninterruptedly out of the envelope in a terminal lead.

2. The combination according to claim 1, in which said movable contact comprises a conductive metallic ring rollably engaging said one of the contact points.

3. The combination according to claim 1, in which said ground-plane means includes a plurality of radially extending ground potential leads each having a portion within the envelope and a portion outside the envelope, and annular metallic plate means conductively interconnecting the inner end portions of the ground potential leads and capacitively related to the adjacent spaced contact points.

References Cited UNITED STATES PATENTS 2,432,476 12/1947 Hesse 2004 2,477,635 8/1949 Marchand 333--975 2,550,921 5/ 1951 Greene 20016 2,823,358 2/1958 Means et al. 333-97 3,001,046 9/1961 Racz et a1 20087 3,119,911 1/1964 Cherry 200-87 HERMAN KARL SAALBACH, Primary Examiner.

C. BARAFF, Assistant Examiner. 

1. A COAXIAL SWITCH COMPRISING A DIELECTRIC ENVELOPE PORTION CLOSED ON ONE SIDE WITH A METALLIC WALL AND THEREWITH ENCLOSING A HERMETICALLY SEALED CHAMBER, A MAGNETIC CORE FIXED ON THE METALLIC WALL AND HAVING ONE END ADJACENT THERETO, AN ARMATURE PIVOTALLY MOUNTED WITHIN THE CHAMBER ADJACENT ONE END OF THE CORE, MEANS PRESSING THE ARMATURE IN A DIRECTION AWAY FROM THE CORE, MEANS ADJACENT THE END OF THE CORE REMOTE FROM THE ARMATURE OPERABLE TO MOVE THE ARMATURE IN A DIRECTION TOWARD THE CORE, SPACED CONTACT POINTS WITHIN THE CHAMBER MOUNTED ON THE DIELECTRIC ENVELOPE PORTION, EACH SAID POINT BEING CONTINUOUS WITH A LEAD EXTERNAL TO THE ENVELOPE PORTION, 